International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

© International Union of Crystallography 2006
International Tables for Crystallography (2006). Vol. C. ch. 9.6, p. 812

Section 9.6.2.1. Selection of crystallographic data

A. G. Orpen,a L. Brammer,b F. H. Allen,c D. G. Watsonc and R. Taylorc

a School of Chemistry, University of Bristol, Bristol BS8 1TS, England,bDepartment of Chemistry, University of Missouri–St Louis, 8001 Natural Bridge Road, St Louis, MO 63121-4499, USA, and cCambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England

9.6.2.1. Selection of crystallographic data

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All results given in Table 9.6.3.3[link] are based on X-ray and neutron diffraction results retrieved from the September 1985 version of the CSD. Neutron diffraction data only were used to derive mean bond lengths involving hydrogen atoms. This version of the CSD contained results for 49 854 single-crystal diffraction studies of organo-carbon compounds; 9802 of these satisfied the acceptance criteria listed below and were used in the averaging procedures:

  • (i) Structure contains a d- or f-block metal.

  • (ii) Atomic coordinates for the structure have been published and are available in the CSD.

  • (iii) Structure was determined from diffractometer data.

  • (iv) Structure does not contain unresolved numeric data errors from the original publication (such errors are usually typographical and are normally resolved by consultation with the authors).

  • (v) Only structures of higher precision were included on the basis that either (a) the crystallographic R factor was ≤ 0.07 and the reported mean estimated standard deviation (e.s.d.) of the C—C bond lengths was ≤ 0.030 Å (corresponds to AS flag = 1, 2 or 3 in the CSD), or (b) the crystallographic R factor ≤ 0.05 and the mean e.s.d. for C—C bonds was not available in the database (AS = 0 in the CSD).

  • (vi) Where the structure of a given compound had been determined more than once within the limits of (i)–(v), then only the most precise determination was used.

The structures used in Table 9.6.3.3[link] do not include compounds whose structure precludes them from the CSD (i.e. not containing `organic' carbon). In practice, structures including at least one C—H bond are taken to contain `organic' carbon. Thus, the entry for Cr—CO distances has a contribution from [NEt4][Cr(μ-H)(CO)10] but not from K[Cr(μ-H)(CO)10] or [Cr(CO)6].








































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